WASHINGTON (Reuters) - Federal Reserve Chair Janet Yellen was hospitalized over the weekend to treat a urinary tract infection while she was vacationing with her family in London, the Fed said in a statement on Monday.

"She was admitted Friday and released Monday," the Fed said. "She is returning to Washington, D.C., and expects to resume her schedule as planned this week."

It was unclear how serious Yellen's condition was.

Yellen, who is 70 years old and the most powerful figure in world finance, had a health scare in 2015, receiving emergency medical attention following a speech during which she appeared to lose concentration. Following that episode, the Fed said Yellen felt dehydrated after speaking for nearly an hour.

There was no indication of any relation between the two health incidents.

Last week, Yellen was in London for a conference on Tuesday and then stayed in the city for a vacation with her family, according to the Fed statement.